2026/03/31 by SungWon Kwak, Ivan Minchev, Matthias Steinmetz +1
Physics and Astronomy · #Galaxies: Formation, Evolution, Phenomena #Astronomy and Astrophysical Research #Stellar, planetary, and galactic studies
paper · pdf · doi:10.1051/0004-6361/202659676
Using N-body simulations, we examined the impact of dark matter (DM) halo resolution and gravitational softening on bar formation. We generated isolated disk-halo systems with fixed stellar disk parameters, varying the number of halo particles, softening lengths, and halo concentration to modulate disk stability via the central DM fraction. The effects of DM resolution (mratio=1, 10, and 100) on bar formation are less pronounced in more unstable disks, in which the overall evolutionary path is similar except that the lowest DM resolution model suffers gradual bar weakening. Irrespective of the halo resolution, large softening, epsdm, flattens the central halo density profile within the softening scale, impeding angular momentum transfer to the nascent bar and preventing bar formation in more stable models. In unstable models with epsdm=0.96 , ̨pc, a small bar still emerges due to enhanced initial instability and a larger seed perturbation, yet the bar strength F2 remains capped around 0.3 owing to unresolved central dynamical friction. Despite the destabilizing effect of the reduced central DM fractions, our results indicate that deficient central angular momentum exchange can still suppress bar growth. Furthermore, halo softening influences buckling instability, as larger values (epsdm=0.30 and 0.60 , ̨pc) inhibit central vertical heating, exacerbating radial-vertical velocity dispersion anisotropies and triggering stronger buckling. We recommend adopting łe 10 , łeq 104 , , and < 0.30, when investigating the formation and evolution of non-axisymmetric structures in Milky Way-mass galaxies. kpc